I cannot minimise or move any of my plot window in my Mac installation of ioGAS.

This is a known issue with the plot window GUI in the 6.0 and 6.0.1 version of the ioGAS software. We are working on a solution for this issue that will be introduced in ioGAS version 6.1. In the meantime, you will need to use ioGAS 5.2 to use the full functionalities of the plot’s minimise/close fuctions.